Stabilizing the Blood-Brain Barrier Against Invading Parasites

African trypanosomes, a brain-infecting parasite, surrounded by red blood cells. Image Credit: Centers for Disease Control and Prevention

When it comes to defending the brain from parasites, the immune system, if not kept under tight control, can actually do more harm than good. The brain is immunologically privileged: it is protected from outside threats by both the blood-brain barrier, a tightly-packed layer of cells that allows only certain molecules to enter the brain from the bloodstream, and by specialized immune cells located inside the barrier. When the brain comes under siege by parasites, immune cells from the bloodstream are recruited to the area to help attack the invaders. This flooding of immune cells into the tissue surrounding the brain damages the cells in the blood-brain barrier, inadvertently allowing more parasites into the brain. Olivera et al. show that nitric oxide helps prevent immune cells from overwhelming the blood-brain barrier. When immune cells first reach the brain from the bloodstream, they stimulate immune cells in the brain to produce nitric oxide. As more nitric oxide is produced, it inhibits signaling molecules that would normally recruit additional immune cells to the brain. This negative-feedback loop ensures that some immune cells arrive to provide additional defenses for the brain, but not so many that damage is caused to the fortification keeping the parasites at bay.

- Stephanie DeMarco
Staff Writer, Signal to Noise Magazine
PhD Candidate, Molecular Biology

 

Bacterial Infection During Pregnancy May Lead to Neurodevelopmental Disorders

Image Credit:
Embryo week 9-10” by Lunar Caustic is licensed under CC by 2.0

Our immune systems have evolved to recognize certain foreign molecules that are similar in many species of bacteria, such as parts of the bacterial cell wall. Although these immune mechanisms are built to protect us from foreign invaders, the inflammation and cell proliferation that result from exposure to pathogenic bacteria can actually be detrimental to our health if excessive. In a new study, Humann and colleagues have demonstrated for the first time that bacterial cell wall components can cross a mother’s placenta into the developing fetal brain, where they are recognized by the fetus’s immune sensors. The resulting proliferation of fetal neurons can lead to developmental disorders in the fetal brain. This work has important implications for how we treat pregnant women with bacterial infections, as some antibiotics that work by rupturing bacterial cells are more likely to release these harmful components into the bloodstream, while other antibiotics that kill bacteria without lysing them may lead to less inappropriate inflammation and neuron proliferation in the unborn fetus.

- Jeff Maloy
Staff Writer, Signal to Noise Magazine

PhD Candidate, Microbiology



Reference:
Humann, J., et al. (2016). “Bacterial Peptidoglycan Transverses the Placenta to Induce Fetal Neuroproliferation and Aberrant Postnatal Behavior.” Cell Host & Microbe. 19(3): 388-399.

Across the Bench with Amanda Freise

Across the Bench with Amanda Freise

In the Wu Lab (part of the Crump Institute for Molecular Imaging at UCLA), researchers are working to find new ways to diagnose immune diseases by studying the way that disease develops in healthy tissues. The goal is to find painless, non-invasive ways to identify diseased cells in patients. I sat down with Amanda Freise, a graduate student researcher in the Wu Lab, to understand just how that works.

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